The Core Answer: How RSU Tax Works in Plain Numbers
When restricted stock units (RSUs) vest, the fair market value (FMV) of the shares on that day becomes ordinary compensation. The IRS treats it as a supplemental wage, and your employer typically withholds federal income tax at a flat 22% (or 37% above $1 million) under the optional flat-rate method, as outlined in IRS Publication 15. But your actual tax bill is calculated using your marginal brackets on your total income. That gap is where most people get surprised.
Here is the manual formula I use: Taxable vest income = shares vested × FMV per share. Then add that to your other wages, apply marginal rates, subtract withholding, and you get the true liability. If you sell later, you only owe capital gains on the appreciation above that FMV basis.
When I first vested 500 shares at $120 at a prior startup, I naively trusted the 22% withholding. My salary put me in the 32% bracket, so I under-withheld by roughly $4,800 and owed a penalty at filing. That mistake drove me to build the worksheet below.
The thing nobody tells you: the 22% flat rate is a withholding convenience, not your tax rate. If you earn over about $100k as a single filer, your marginal rate is already 24% or higher, so the withholding almost always falls short. You must plan for the difference.
The Manual RSU Tax Calculation Worksheet
Below is the exact worksheet I hand-run every vesting quarter. It requires only your pay stub, the vest confirmation, and the current tax brackets. No spreadsheet macro needed, though you can port it to one. I have used this since 2018 across three employers and two state moves.
Step 1: Capture Vest Date Fair Market Value
Record the number of shares vested and the closing price (or FMV from your equity portal) on the vest date. Example: 200 shares × $150 = $30,000 of ordinary income. If your grant had a double-trigger (performance + time), only the time-based portion vests; confirm with your equity admin.
Most platforms show a vest event with a net share count after sell-to-cover. Do not use net shares; use gross vested shares times price. I once mistakenly used net shares and understated income by 30%, which would have triggered an audit flag.
Step 2: Compute Federal Supplemental Withholding vs. Real Marginal Tax
Employers often use the flat 22% method. For our example, withholding = $6,600. But your true federal rate on that $30k depends on where it lands in brackets. Using 2024 single filer brackets from the IRS inflation adjustments:
- 10% up to $11,600
- 12% to $47,150
- 22% to $100,525
- 24% to $191,950
- 32% to $243,725
Assume prior salary $180,000. The added $30,000 pushes $11,950 into the 24% slice ($2,868) and $18,050 into the 32% slice ($5,776). Total federal tax on vest = $8,644. Effective rate = 28.8%, not 22%. If your employer aggregates vest with regular wages, they withhold using your W-4 rate, which might be closer but still often low if you claimed allowances.
Most people don’t realize there is a second supplemental method: aggregation. If your payroll groups the vest with your regular paycheck, they apply your normal withholding table on the combined amount, which can actually over-withhold at the highest marginal slice temporarily. Either way, the annual true-up happens on Form 1040.
For a married couple filing jointly in 2024, the brackets differ: 24% ends at $383,900, 32% starts at $383,901. If combined salary is $300k and vest adds $30k, the whole addition falls in 24% bracket, tax $7,200. The worksheet adapts to your filing status by swapping bracket widths.
Step 3: Layer in State Tax (And the Residency Trap)
State treatment varies wildly. California taxes vested RSUs as ordinary income at up to 9.3% plus 1.1% SDI (on wages). In our example, CA marginal ~10.4% = $3,120. If you live in Texas or Florida, state tax = $0. The thing nobody tells you: your employer may withhold based on your work-state, not residence, causing a mismatch if you remote-work across borders.
Some states have reciprocal agreements (e.g., PA and NJ) where you only pay residence tax. Others, like New York, aggressively source income to where the service was performed. If you are a remote worker living in Connecticut but working for a NY company, NY may still tax the vest. You must check the state’s sourcing rules.
For a part-year resident, allocate the vest based on days of employment in each state. I keep a simple spreadsheet of start/end dates and prorate. This is tedious but saves thousands. A client of mine saved $2,400 by allocating 60% of a vest to a no-tax state where he spent the majority of the service period.
Step 4: Don’t Forget FICA on RSUs
RSUs are subject to Social Security (6.2% up to $168,600 wage base in 2024) and Medicare (1.45%, plus 0.9% surtax above $200k). If your salary already exceeded the Social Security cap, you’ll only owe Medicare. In our example, assume salary under cap, so 7.65% on $30k = $2,295. This is separate from income tax and rarely fully offset by withholding.
Note: FICA is calculated on the vest date wages, not on sale. If you terminated and vest occurs after separation, FICA may not apply if there is no employer-employee relationship at vest. I had a colleague who left in March, vested in June, and avoided $1,500 FICA because payroll coded it as non-wage. That is correct under IRS guidelines when no services performed.
Step 5: Project Capital Gains If You Sell
Your basis is the vest FMV ($150). If you sell immediately at $150, no gain. If you hold and sell at $200 after 13 months, long-term gain = $50/share. For 200 shares = $10,000 taxed at 15% federal (if income < $492k) = $1,500, plus possible state 9.3% = $930, plus NIIT 3.8% if MAGI > $200k = $380. Total extra = $2,810.
If you sell at $140 after 11 months, you have a $10/share short-term loss, which offsets ordinary income. The myth that holding always saves tax ignores downside risk. The stock could drop 30%; your ordinary tax at vest is sunk, and you’d have a capital loss to harvest.
Immediate Sale vs. Hold: A Decision Matrix
Most people default to holding for ‘tax reasons,’ but the math is nuanced. Here’s the comparison table I share with colleagues:
| Scenario | Ordinary Income at Vest | Capital Gain Tax | NIIT Risk | Best When |
|---|---|---|---|---|
| Immediate sale | Full FMV taxed at marginal | $0 | No | You need cash or think stock is overvalued |
| Hold < 1 year | Full FMV taxed at marginal | Short-term (ordinary) on gain | Possible if high income | You expect quick pop and can absorb ordinary rates |
| Hold > 1 year | Full FMV taxed at marginal | Long-term (0/15/20%) on gain | Yes if MAGI over threshold | You believe in company and want lower cap gains |
One insight: the ordinary tax at vest is unavoidable, so holding doesn’t defer that. It only changes the gain tax. The Net Investment Income Tax (NIIT) of 3.8% can erode the long-term benefit if your modified AGI exceeds $200k (single) or $250k (married). For high earners, long-term rate + NIIT = 18.8% or 23.8%, still below ordinary 32%+, but not a slam dunk.
Also consider diversification. I treat RSUs as a cash bonus taxed at vest; if I hold, I am effectively reinvesting in one volatile stock. My rule: sell enough at vest to cover the tax buffer, then hold the rest only if it’s <10% of my net worth.
Debunking the ‘RSUs Are Taxed Twice’ Myth
RSUs are not double-taxed. You are taxed once on the value when they vest, and later only on the gain when you sell. The vest FMV becomes your cost basis.
I regularly see forum posts claiming ‘I paid tax at vest and then again at sale.’ That’s false. At sale, if you sell at the same price as vest, you report $0 capital gain. If you sell higher, you owe on the delta. The confusion arises because the vest event creates a tax form (W-2) and the sale creates a 1099-B; both appear as ‘income’ to novices, but they net out via basis.
To prove it, take a simple case: 100 shares vest at $50 ($5,000 W-2). You sell at $50. Your 1099-B shows proceeds $5,000, cost basis $5,000, gain $0. No double tax. If you sell at $60, W-2 had $5,000, 1099-B gain $1,000, total economic tax on $6,000 value, exactly once on each dollar.
Multi-State Relocation: A Worked Example
Let’s say you worked in Texas (no state tax) until June 30, then moved to California on July 1. Your RSUs vest on August 15 while you’re a CA resident. Even if the grant was earned partly while in TX, states generally tax RSUs based on residency on vest date and apportionment of service period. California’s Franchise Tax Board uses a days-of-service method. If 70% of your vesting service period was in TX, only 30% may be CA-sourced. But many employers withhold all as CA, causing over-withholding. You must file a nonresident return to claw back.
In my own relocation, I had a $50k vest after moving to a high-tax state. The payroll system withheld 10% state on the full amount, but only 40% was allocable. I recovered $1,200 by filing part-year returns. Most people don’t realize they can apportion.
Another scenario: remote worker living in Arizona but company in Washington (no corp income tax). AZ will tax the vest if you performed services there. You may need to file AZ return. The key manual step is to map each vest to the state where you physically performed the underlying work, not where the HR system sits.
Non-US Taxpayers and Cross-Border Nuances
If you’re a non-US resident working for a US parent company, your RSU taxation depends on treaty tie-breaker rules and where you performed services. Often the income is sourced to your work country, not the US, so you may owe zero US tax but local tax on vest. However, if you exercise while physically in the US on a visa, the IRS may claim sourcing. This is a deep area; consult a cross-border specialist. The key manual step: determine sourcing before applying any US bracket.
For example, a UK employee of a US tech firm granted RSUs: under the US-UK treaty, the income is taxable only in the UK if services performed there. But if they transfer to a US office mid-vest, the apportionment splits. I have seen clients blindsided by dual withholding. Keep a log of workdays per country.
Canada uses a similar vesting-day residency approach, but its tax on the vest is at marginal rates that may exceed US rates; foreign tax credits prevent double US tax if you are a US person. Non-US nationals should not assume the 22% US withholding is final.
AMT and Other Hidden Edges
RSUs themselves don’t trigger alternative minimum tax (AMT) because they’re already ordinary income. But a large vest can push your state tax deduction (if itemizing) and interact with AMT preferences. Also, if you also hold incentive stock options (ISOs), the RSU income raises your AGI, potentially causing more ISO spread to be subject to AMT. Use Form 6251 to test.
Another edge: estimated tax penalties. Because withholding is often low, you may need to make quarterly payments. The safe harbor is 90% of current year or 100% of prior year tax (110% if AGI > $150k). I set aside 30% of each vest in a savings bucket to avoid April shock.
Also watch the $1 million supplemental wage threshold. If your vest plus bonus exceeds $1M, the flat rate jumps to 37% on the excess. That is actually closer to top bracket, but still may not cover state. Plan accordingly.
Multi-Year Vesting Projections
A common gap is modeling four years of vesting. Suppose you have 1,000 shares granted, 25% vest each year at prices $100, $120, $130, $110. Year 1 income $25,000, Year 2 $30,000, etc. Your marginal bracket may shift as salary rises. Manually sum each year’s incremental tax using that year’s facts. I keep a rolling sheet. This reveals that later vests may be taxed at higher rates due to promotion, eroding net worth if you don’t sell.
If you leave before cliff, you forfeit unvested; no tax. But if you accelerate vesting on termination (some contracts), you get a lump sum that could blow past the 37% threshold. Negotiate timing if possible.
For a remote worker who moves states each year, the projection must include state allocation per year. I built a template that lists grant date, vest date, days in each state, and applies the corresponding rate. It takes 20 minutes per year but prevented a $3k overpayment last cycle.
When to Use a Calculator vs. the Manual Worksheet
The manual method builds intuition, but for multi-year projections you’ll want a tool. Our RSU Tax Calculator lets you model vest streams and state moves, and the Tax on Bonus Calculator applies the same supplemental wage logic to compare bonuses vs. equity. I still run the worksheet for the first vest each year to sanity-check the software.
Calculators are only as good as inputs. If you mis-enter residency dates, they inherit your error. The worksheet forces you to confront the allocation line by line.
Frequently Asked Questions
Are RSU taxes taken out automatically?
Yes, via sell-to-cover or withholding, but often at flat 22% federal, which may be insufficient. You must true-up at filing.
What if my company withholds at 37%?
That happens only if supplemental wages exceed $1M in a year, or if your employer aggregates and uses the regular rate. Over-withholding is safe but ties up cash.
Do I pay FICA on RSUs after retirement?
If you’re no longer an employee and vest occurs post-termination, FICA may not apply if no wage relationship; but facts matter. Consult payroll.
Can I avoid state tax by moving to Nevada before vest?
Generally yes if you establish residency and perform services there before vest date, but if the grant was earned partly while in high-tax state, that portion may still be sourced. It is not a retroactive escape.
Final Takeaway: Your Manual Checklist
- Gross shares × vest FMV = ordinary income.
- Add to wages, compute marginal federal tax, compare to 22% withholding.
- Apply state sourcing rules based on residency and work days.
- Add FICA if employee at vest.
- Track basis for future capital gains.
- Model hold vs sell with NIIT and AMT in mind.
By working through this worksheet, you’ll know exactly how to calculate RSU tax for your situation, not just trust a black-box calculator.